The Hormone Core will provide established and state-of-the-art methods for measuring hormones and biochemical markers of bone turnover. These measurements will be done in the Mayo Foundation Immunochemical Core Laboratory (Mayo ICL), which is a specialized laboratory which provides dedicated immunochemical testing for both clinical and basic research through Mayo Foundation. The ICL laboratory provides the majority of the tests to support Mayo's General Clinical Research Center (GCRC). The availability of the expertise and equipment in the Hormone Core for the performance of the assays needed in this grant proposal is critical to the conduct of the proposed studies.